// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_AUDIO_RENDERER_MIXER_H_
#define MEDIA_BASE_AUDIO_RENDERER_MIXER_H_

#include <stdint.h>

#include <map>
#include <memory>
#include <string>

#include "base/macros.h"
#include "base/synchronization/lock.h"
#include "base/time/time.h"
#include "media/base/audio_converter.h"
#include "media/base/audio_renderer_sink.h"
#include "media/base/loopback_audio_converter.h"

namespace media {

// Mixes a set of AudioConverter::InputCallbacks into a single output stream
// which is funneled into a single shared AudioRendererSink; saving a bundle
// on renderer side resources.
class MEDIA_EXPORT AudioRendererMixer
    : NON_EXPORTED_BASE(public AudioRendererSink::RenderCallback) {
public:
    typedef base::Callback<void(int)> UmaLogCallback;

    AudioRendererMixer(const AudioParameters& output_params,
        scoped_refptr<AudioRendererSink> sink,
        const UmaLogCallback& log_callback);
    ~AudioRendererMixer() override;

    // Add or remove a mixer input from mixing; called by AudioRendererMixerInput.
    void AddMixerInput(const AudioParameters& input_params,
        AudioConverter::InputCallback* input);
    void RemoveMixerInput(const AudioParameters& input_params,
        AudioConverter::InputCallback* input);

    // Since errors may occur even when no inputs are playing, an error callback
    // must be registered separately from adding a mixer input.  The same callback
    // must be given to both the functions.
    void AddErrorCallback(const base::Closure& error_cb);
    void RemoveErrorCallback(const base::Closure& error_cb);

    void set_pause_delay_for_testing(base::TimeDelta delay)
    {
        pause_delay_ = delay;
    }

    OutputDeviceInfo GetOutputDeviceInfo();

    // Returns true if called on rendering thread, otherwise false.
    bool CurrentThreadIsRenderingThread();

    const AudioParameters& GetOutputParamsForTesting() { return output_params_; };

private:
    class UMAMaxValueTracker;

    // Maps input sample rate to the dedicated converter.
    using AudioConvertersMap = std::map<int, std::unique_ptr<LoopbackAudioConverter>>;

    // AudioRendererSink::RenderCallback implementation.
    int Render(base::TimeDelta delay,
        base::TimeTicks delay_timestamp,
        int prior_frames_skipped,
        AudioBus* audio_bus) override;
    void OnRenderError() override;

    bool is_master_sample_rate(int sample_rate)
    {
        return sample_rate == output_params_.sample_rate();
    }

    // Output parameters for this mixer.
    const AudioParameters output_params_;

    // Output sink for this mixer.
    const scoped_refptr<AudioRendererSink> audio_sink_;

    // ---------------[ All variables below protected by |lock_| ]---------------
    base::Lock lock_;

    // List of error callbacks used by this mixer.
    typedef std::list<base::Closure> ErrorCallbackList;
    ErrorCallbackList error_callbacks_;

    // Each of these converters mixes inputs with a given sample rate and
    // resamples them to the output sample rate. Inputs not reqiuring resampling
    // go directly to |master_converter_|.
    AudioConvertersMap converters_;

    // Master converter which mixes all the outputs from |converters_| as well as
    // mixer inputs that are in the output sample rate.
    AudioConverter master_converter_;

    // Handles physical stream pause when no inputs are playing.  For latency
    // reasons we don't want to immediately pause the physical stream.
    base::TimeDelta pause_delay_;
    base::TimeTicks last_play_time_;
    bool playing_;

    // Tracks the maximum number of simultaneous mixer inputs and logs it into
    // UMA histogram upon the destruction.
    std::unique_ptr<UMAMaxValueTracker> input_count_tracker_;

    DISALLOW_COPY_AND_ASSIGN(AudioRendererMixer);
};

} // namespace media

#endif // MEDIA_BASE_AUDIO_RENDERER_MIXER_H_
